The writing, the subject matter, and the description presented herein is protected under the provisions of United States Copyright laws by the Assignee, International Business Machines Corporation, except only to any extent required by law in order to obtain and to continue all patent protection that is available during the term of any patent that issues hereon.
1. Field of the Invention
The present invention, generally, relates to a technique for imaging an area in contact with a reference surface and, more particularly, to imaging an area with objects of interest having a length scale measurement in microns.
Clearly, the technique of the present invention includes a principal optics, such as possibly but not necessarily a microscope which adds an unanticipated complication. For a microscope type of viewing optics to be effective in forming a useful image, it must involve sufficient light gathering power, and the present invention provides a solution to this complication also.
2. Description of the Prior Art
U.S. Pat. No. 5,734,475 to Pai dated Mar. 31, 1998 describes measuring the density of elements on a wiring board by directing a light to obtain a distance from a reference plane.
U.S. Pat. No. 5,621,530 to Marrable, Jr. dated Apr. 15, 1997 describes measuring distance by directing light between two mirror surfaces arranged at angles and a flat transparent surface.
U.S. Pat. No. 5,465,152 to Bilodeau et al. dated Nov. 7, 1995 describes a method of measuring coplanarity of an array of elements using reflected radiation and 3-D optical sensing.
U.S. Pat. No. 5,450,206 to Caillat et al. dated Sep. 12, 1995 describes using a light beam reflected from balls on a chip and determining conformity of the reflected beam.
U.S. Pat. No. 4,728,186 to Eguchi et al. dated Mar. 1, 1988 describes obtaining data on an uneven surface in contact with a transparent plate using light reflected through the plate.
While at first appearance, the techniques, the apparatus and the methods described in these prior patents have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail presently, are important for the effective use of the invention to achieve the various advantages it provides.
It is an important object of the present invention to provide a technique that permits obtaining a dramatic improvement in the resolution of detail of a contact surface.
It is also an object of the invention to provide a technique to distinguish differences in contact body hardness.
Briefly, an examination of electrical contacts requires determining the number and the distribution of the contact points available for contact. In today""s equipment, this determination involves contact asperity of micron dimensions or less. The contact is pressed against an optical surface while viewing the contact permitting contact points to be imaged and measured.
The above and other objects, features and advantages of the present invention will become more readily apparent as the detailed description of the presently preferred embodiment proceeds.